[ogsa-wg] Taverna workflows

[Donal K. Fellows]

It's been an action on me to find out about Taverna. Since the workflow
session today was cancelled (national holidays? pah!) I'll report what
I've learned so far here before I forget due to vacation. :-)

Taverna is a data-oriented workflow system (as opposed to
control-oriented, though it also supports control links between
processors) for automating tasks as seen from the client-side; it's
intended to replace "human workflows" which involved cutting and pasting
chunks of text between web pages (previously a time-consuming and
error-prone process). It's not designed to handle cases with complex
recovery from failures, but is instead focussed on automated handling of
sets of data. It's GUI-oriented (though there is a command-line
execution module) and as such it has got a number of features to enable
scaling of the complexity of workflows to scientifically-useful levels:
in particular, it has recursive decomposition and a way to mark
processing nodes as "not interesting" and hence normally hidden. One
limitation is that Taverna essentially assumes that the processing nodes
are free to use (both by the user *and* by anyone else) which has a
consequence in terms of its (non-existent) security model[*]. It's also
not designed with dynamic instantiation of services in mind (there's a
plugin for service discovery, but it's not integrated into the workflow
system itself, just the GUI design tool).

In short, if you're doing scientific workflows that use local components
and free static services available over the web, Taverna is very good.
But it's got substantial weaknesses for domains where services are
secured, costly or dynamic. Far more information than I've mentioned is
available online at
    http://taverna.sourceforge.net/index.php?doc=docroot.html

I hope this is informative. :-)

Donal.
[* I understand that there's work ongoing to add some kind of security
    support, but I don't know how that's progressing. It's not in the
    latest production release for sure. ]